Internet Protocol (IP) has become a popular communications standard enjoying wide-scale deployment and use. For example, the Internet is now a worldwide network of communications equipment and service providers which use IP as a common signaling protocol for communicating. On the Internet, messages are transmitted from one user to another over a vast infrastructure of routers, servers, gateways and communication devices. Typically, users on either end of the network operate computers equipped with appropriate software and equipment. The underlying link level protocols handle the messaging functions on both ends of the communication channel.
Transmission Control Protocol/Internet Protocol (TCP/IP) is a connection-oriented transport layer protocol that uses IP as its underlying networking protocol. TCP governs the exchange of sequential data, while IP routes outgoing and recognizes incoming messages. TCP has recently been joined by Stream Control Transmission Protocol (SCTP) as a transport protocol for telephony applications.
The widespread use of IP as a networking protocol has led to an intense push for the integration of IP-based services with other networks such as common channel signaling systems, asynchronous transfer mode networks, and wireless. A form of common channel signaling is channel signaling system number 7 (SS7 or C7) which is a global standard for telecommunications defined by the International Telecommunication Union (ITU) and specifically the Telecommunications Standardization Section of the ITU (ITU-T). While IP networks communicate using flexible and easily modifiable connections, SS7 uses a dedicated network to carry signaling traffic. In essence, the SS7 standard defines the procedures and protocols by which network elements in the public switch telephone network (PSTN) exchange information over a digital signaling network including wireless (e.g. cellular), and wireline call setup, routing and control. The ITU definition of SS7 allows for variance of the procedures and protocols such as those promulgated by the American National Standards Institute (ANSI) and Bell Communications Research (Bellcore) standards used in North America as well as the European Telecommunication Standards Institute (ETSI) standards used in Europe.
Essentially, an SS7 network and the defined protocols are used for implementing call signaling functions including basic call setup management and tear down. In addition, SS7 specifies various wireless services such as personal communication services (PCS), wireless roaming and mobile subscription authentication. Recently, the SS7 protocol has been used for local number portability (LNP) as well as toll free and toll wireline services. Other services that benefit from the SS7 protocol include enhanced call features such as call forwarding, calling party name and number display and three way calling as well as a wide array of emerging applications standards that provide for efficient and secure worldwide telecommunication.
With an SS7 network, messages are exchanged between network elements over 56 or 64 kilobits per second (kbps) using bi-directional channels called signaling links. Signaling occurs-out-of-band on dedicated channels rather than in-band on voice channels. Compared to in-band signaling, out-of-band signaling provides faster call setup times, more efficient use of voice circuits, and support for intelligent network services which require signaling to network elements without voice trunks. In addition, out-of-band provides for improved control over fraudulent network use. These advantages have made the SS7 protocol a popular choice for telephony.
The hardware and software functions of the SS7 protocol are divided into functional abstractions called levels. These levels map loosely to the Open Systems Interconnect (OSI) 7-layer model defined by the International Standards Organization (ISO). An Integrated Services Digital Network (ISDN) user part (ISUP) defines the protocol used to setup, manage and release trunk circuits that carry voice data between terminating line exchanges, e.g., between a calling party and a called party.
Currently, SS7 requires a dedicated network to handle the transport of signaling traffic. Some effort has been made to try to utilize other network resources, like an IP-based network, for transferring SS7 signaling traffic in an attempt to offer load sharing and save costs associated with deploying and utilizing a specialized, dedicated network. The internetworking between SS7 signaling traffic and IP is provided by a gateway that includes the conversion mechanism between the two protocols.
One such solution is offered by the company Tekelec which manufactures and sells a gateway capable of communicating SS7 signaling traffic over an IP network. The Tekelec product uses a proprietary signaling protocol known as Transport Adapter Level Interface (TALI) that is designed to use standard TCP as the transport layer. In addition, the Tekelec solution requires a smart STP to properly route SS7 signaling traffic over the IP network. This requires that traffic be routed to an intermediary node in the IP network resulting in an additional hop for messages to reach their destination.
Thus, with prior art SS7/IP signaling mechanisms, a message must first go from an origination Signaling Gateway (SG) on the edge of the IP network to a “smart” Signal Transfer Point (STP). The SG transports the SS7 message to the STP using IP and the STP interprets the SS7 message and routes it to its destination. Thus, the smart STP routes the message to a destination Signaling Gateway at the border of the IP network which recovers the SS7 signaling traffic from the IP message stream. Thus, since a dedicated conversion node is needed, the signal traffic must traverse an extra hop in the transmission pathway resulting in unnecessary delay and complexity of a dedicated network path and conversion node. Moreover, the use of a proprietary IP protocol, such as TALI, is disadvantageous since it limits inter-networking between equipment not supporting the protocol in the network.
Accordingly, a way of routing SS7 signaling traffic over IP that is free of proprietary protocols and that eliminates the need for a dedicated conversion node would provide numerous advantages.